1. Field of the Invention
This invention concerns hydraulic couplings used in subsea oil and gas well applications. More particularly, it relates to junction plates used to simultaneously mate a plurality of male and female hydraulic couplings.
2. Description of the Related Art
Offshore oil and gas exploration and production involves the placement of numerous valves and safety equipment on or near the sea floor. The collection of such equipment on a well is often referred to as a “tree.” Frequently, these devices are hydraulically actuated from a remote location such as a production platform. A bundle of hydraulic lines, known as an umbilical cable, is routed from a control panel on the platform to the subsea tree. For ease of assembly and maintenance, subsea hydraulic couplings are typically provided for joining the hydraulic lines to the tree. Examples of such subsea hydraulic couplings are disclosed in U.S. Pat. No. 6,626,207 and U.S. Pat. No. 6,375,153.
Because such couplings must be mated underwater by divers or remotely operated vehicles (“ROVs”), it has been found that the mating process may be expedited by placing a plurality of couplings on opposing junction plates. The junction plates hold the couplings in position and are provided with means for securing the two plates in proximity one to another so as to maintain the individual couplings in a connected condition. Since the hydraulic lines may be pressurized with hydraulic fluid at or about 17,500 psi, the junction plates must be able to withstand the force of the hydraulic fluid acting on the male members as they are inserted into the receiving chambers of the female members and the poppet valves open to allow the flow of hydraulic fluid. It is accordingly necessary to provide some means of mechanical advantage to bring the plates into the fully coupled position.
Male or female couplings may be provided on either plate, but it is typical to locate the male couplings on the fixed plate and the female couplings on the removable plate because the female couplings most often contain the sealing elements and it facilitates the replacement of those sealing elements by having them on a recoverable device—i.e., the plate holding the female members may be brought to the surface for maintenance operations.
Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with sealed fluid passageways connecting therebetween. The female member generally is a cylindrical body with a relatively large diameter longitudinal bore at one end and a relatively small diameter longitudinal bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore seals and slidingly engages the male member of the coupling.
The male member includes a cylindrical body with a probe section approximately equal to the diameter of the female member bore, and a connection at its other end to facilitate connection to hydraulic lines. When the probe section of the male member is inserted into the bore of the female member, according to various embodiments of the device, fluid flow is established between the male and female members.
A male member and female member are generally connected to opposing junction plates of a manifold and are held together by bolts or hydraulic members attached to the plates. The male member is commonly attached to one junction or manifold plate, while the female member is attached to an opposing plate so as to face the male member and align with it. The male and female members may be attached to the junction plates or manifold plates using various means, such as set screws or threads. Techniques for attaching the members to such plates are well known to those skilled in the art.
Typically, several subsea hydraulic connectors are grouped together on each junction or manifold plate. For example, two or more coupling members may be attached to each opposing plate. In the subsea environment, a diver or remotely operated vehicle is used to connect the opposing plates together, and thereby connect the opposing coupling members on each of the plates. The coupling members are typically simultaneously connected and the opposing plates are locked together.
High separational forces are transferred to the opposing junction plates, due to the separational forces of the high pressure hydraulic fluid in each coupling member. In many cases, the plates must be relatively thick and heavy in order to withstand high separational forces. The plates are typically stainless steel and between one and one and one-half inches in thickness.
The prior art describes various means for joining two junction plates. For example, U.S. Pat. No. 5,265,980 describes a junction plate assembly for a subsea structure having a connector shaft with external acme threads which mates with an internally threaded second junction plate. A handle is connected to an opposite end of the shaft for rotating the shaft by hand. Alternatively, the shaft may be equipped with a connection for an ROV.
U.S. Pat. No. 4,915,419 to Robert E. Smith III relates to a sliding lock plate for locking together simultaneously male and female coupling members on opposing junction plates. Various other locking devices have been used or proposed to lock together the male and female coupling members attached to junction plates. These locking devices lock the coupling members together after the male end coupling members are fully engaged, and do not assist in bringing the male and female members together into full engagement before locking. In many cases, substantial axial forces are needed to bring all the male coupling members on a junction plate into full engagement with the female coupling members on the opposing junction plate. Hydraulic systems at subsea depths are subject to a number of different forces tending to inhibit the connection of male and female coupling members. For example, subsea pressures at significant ocean depths, high hydraulic pressure in the system, and mechanical forces required to open valves and connect junction plates are among the factors of concern. A combination of these forces may result in difficulty simultaneously engaging the male and female coupling members on opposing junction plates, and also result in substantial separational forces after the coupling members are connected.
Attempts have been made to simultaneously bring the junction plates together, including threaded devices. However, threaded connections have the disadvantages of marine growth buildup in the threads and galling of the threads. Moreover, threaded junction plate connectors typically require multiple turns of the threaded member in order to bring the two junction plates into the fully mated position. This requires time to accomplish and during this time the hydraulic couplings are not fully made up. This presents the opportunity for fluid loss or sea water entry. Another alternative for bringing together subsea hydraulic connectors is lock sleeves. However, lock sleeves are relatively heavy and bulky, which is undesirable in the subsea environment. Other problems are caused by a buildup of silt, ocean debris and marine growth in the lock sleeves. Typically, the lock sleeve systems includes lock sleeves connected to a plate interposed between the male and female junction plates. As the intermediate plate is pulled back, all of the lock sleeves on the coupling members are simultaneously pulled back and then released. The buildup of silt, ocean debris and marine growth may result in jamming the lock sleeves and especially the locking balls.
U.S. Pat. No. 6,471,250 discloses a junction plate assembly for undersea hydraulic couplings that uses a sloped cam surface on one of the junction plates and a central shaft having a cam follower that moves up the sloped cam surface to bring the two junction plates together. This apparatus, however, only provides mechanical advantage for bringing the junction plates closer to one another; no mechanical assist is available for separating the plates—i.e., disconnecting the couplings mounted thereon.
Accordingly, a simple and highly reliable mechanism is needed for simultaneously engaging and disengaging male and female coupling members on junction plates in the subsea environment. What is needed is an apparatus which can both make up and disengage hydraulic connections quickly, with minimal friction. The present invention solves this problem.